William R. Leisher; Innovative Paintings Conservator

William R. Leisher, 51, the paintings conservator who developed the prototype conservation center at the Los Angeles County Museum of Art. A native of Alden, Mich., Leisher earned three degrees in literature and fine arts at the University of Michigan. He began his career as assistant conservator of paintings for the National Gallery of Art in Washington. In 1980, he took over a small conservation office at the Los Angeles County Museum of Art and in the next five years developed it into a model for art museums. Since 1985, Leisher had served as executive director of the conservation department of the Art Institute of Chicago. On Wednesday in Evanston, Ill., of cancer.